Intersubunit movement is required for ribosomal translocation

Translocation of tRNA and mRNA during protein synthesis is believed to be coupled to structural changes in the ribosome. The "ratchet model," based on cryo-EM reconstructions of ribosome complexes, invokes relative movement of the 30S and 50S ribosomal subunits in this process; however, ev...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2007-03, Vol.104 (12), p.4881-4885
Main Authors: Horan, Lucas H, Noller, Harry F
Format: Article
Language:English
Subjects:
Base Sequence
Biological Sciences
Cross-Linking Reagents - pharmacology
Dialysis
Disulfides
Disulfides - metabolism
Escherichia coli - metabolism
Gels
Messenger RNA
Models, Molecular
Molecular Sequence Data
Peptide Elongation Factor G - metabolism
Peptide elongation factors
Protein Biosynthesis - drug effects
Protein synthesis
Protein transport
Reactivity
Ribosomes
Ribosomes - drug effects
Ribosomes - metabolism
RNA, Messenger - genetics
Transfer RNA
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Summary:Translocation of tRNA and mRNA during protein synthesis is believed to be coupled to structural changes in the ribosome. The "ratchet model," based on cryo-EM reconstructions of ribosome complexes, invokes relative movement of the 30S and 50S ribosomal subunits in this process; however, evidence that directly demonstrates a requirement for intersubunit movement during translocation is lacking. To address this problem, we created an intersubunit disulfide cross-link to restrict potential movement. The cross-linked ribosomes were unable to carry out polypeptide synthesis; this inhibition was completely reversed upon reduction of the disulfide bridge. In vitro assays showed that the cross-linked ribosomes were specifically blocked in elongation factor G-dependent translocation. These findings show that intersubunit movement is required for ribosomal translocation, accounting for the universal two-subunit architecture of ribosomes.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0700762104